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On the Damping of Phonograph Arms

The low-frequency resonant rise of a pickup arm may be avoided by placing the resonance frequency below the lowest frequency of interest, which may result in exaggerated rumble; or by damping out the resonance by means of some form of viscous damping. -Dynamic damping- which does not contribute to the steady-state arm drag may be obtained by dividing the arm mass into two portions coupled by viscoelastic means. It is shown in this paper that optimum dynamic damping requires that the mass portion associated with the cartridge be vanishingly small compared to the mass of the arm proper and the counterweight. Some piezoelectric transducers fixed to otherwise undamped arms meet this requirement. Simulated steady-state and transient response characteristics of pickups with various types of damping are presented.